At a glance
Understand the key differences between PGT-A and PGT-M, two types of preimplantation genetic testing used during IVF to screen embryos for chromosomal abnormalities or specific genetic disorders.
PGT-A vs PGT-M: What’s the Difference?
If you’re considering IVF and genetic testing of embryos, you may have come across the terms PGT-A and PGT-M. Both are types of preimplantation genetic testing (PGT), but they serve different purposes. In short, PGT-A screens embryos for an abnormal number of chromosomes (aneuploidy), while PGT-M tests for specific single-gene disorders that one or both parents carry. Understanding the difference can help you have more informed conversations with your fertility clinic about which test, if any, is right for your situation.
At a Glance: PGT-A vs PGT-M
- PGT-A (Preimplantation Genetic Testing for Aneuploidy) checks for extra or missing chromosomes, which are a common cause of implantation failure and miscarriage.
- PGT-M (Preimplantation Genetic Testing for Monogenic Disorders) looks for specific inherited conditions caused by a single gene, such as cystic fibrosis or sickle cell disease.
- PGT-SR (Preimplantation Genetic Testing for Structural Rearrangements) is used when a parent has a chromosomal rearrangement, like a translocation.
- Both tests require IVF and embryo biopsy, and they can be performed together if needed.
What Is PGT-A?
PGT-A is a screening test that evaluates embryos for aneuploidy—having too many or too few chromosomes. A normal human embryo should have 46 chromosomes (23 pairs). Aneuploidy can lead to failed implantation, miscarriage, or conditions like Down syndrome (trisomy 21). PGT-A is often recommended for women of advanced maternal age, couples with recurrent pregnancy loss, or those who have had multiple failed IVF cycles. However, it is not a guarantee of pregnancy or a healthy baby; it simply helps select embryos that are more likely to be chromosomally normal.
What Is PGT-M?
PGT-M is a diagnostic test for specific monogenic disorders—conditions caused by a mutation in a single gene. If you or your partner carry a known genetic mutation, PGT-M can identify embryos that have inherited the disorder, are carriers, or are unaffected. This test is typically used for couples with a known family history of a genetic disease, such as Huntington’s disease, thalassemia, or muscular dystrophy. PGT-M requires prior knowledge of the specific genetic mutation and often involves building a personalized test for each family.
Key Differences Between PGT-A and PGT-M
| Aspect | PGT-A | PGT-M |
|---|---|---|
| Purpose | Screens for chromosomal abnormalities (aneuploidy) | Tests for specific single-gene disorders |
| Who might consider it | Women over 35, recurrent miscarriage, repeated implantation failure | Couples with known genetic mutations or family history |
| What it detects | Extra or missing chromosomes | Specific gene mutations |
| Requires prior genetic information? | No | Yes, the specific mutation must be known |
| Result interpretation | Embryo classified as normal, abnormal, or mosaic | Embryo classified as affected, carrier, or unaffected |
When Is Each Test Recommended?
PGT-A is generally offered to patients who have no known genetic disorder but want to reduce the risk of chromosomal abnormalities. It may be particularly useful for women of advanced maternal age, as the risk of aneuploidy increases with age. PGT-M is recommended when one or both partners are carriers of a genetic mutation that could cause a serious condition in their child. In some cases, both tests are performed together—for example, a couple undergoing PGT-M for a single-gene disorder may also opt for PGT-A to screen for chromosomal issues.
How Do PGT-A and PGT-M Complement Each Other?
PGT-A and PGT-M are not mutually exclusive; they can be used together to provide a more complete picture of an embryo’s genetic status. For instance, a couple with a known genetic mutation might use PGT-M to select embryos free of the disorder, while also using PGT-A to ensure those embryos have the correct number of chromosomes. This combined approach can increase the likelihood of transferring a viable embryo, but it does not guarantee success.
What Are the Limitations of PGT?
It’s important to understand that PGT has limitations. PGT-A cannot detect all genetic abnormalities, and a ‘normal’ result does not guarantee a healthy baby. PGT-M is highly accurate for the specific mutation tested, but it does not screen for other genetic conditions. Additionally, the biopsy process carries a small risk of embryo damage, and not all embryos may survive the testing process. PGT is not a substitute for prenatal testing, and many clinics recommend confirmatory testing during pregnancy.
Questions to Ask Your Clinic
- Which type of PGT do you recommend for my situation, and why?
- What is the accuracy rate for the specific test you offer?
- How many embryos typically survive the biopsy and testing process?
- What are the costs involved, and are they covered by insurance?
- How long does it take to get results?
- What are the risks and limitations of the test?
Next Steps: Making an Informed Decision
- Consult with a fertility specialist to review your medical history and any genetic risks.
- If considering PGT-M, undergo genetic counseling and testing to identify specific mutations.
- Discuss with your clinic whether PGT-A, PGT-M, or both are appropriate for you.
- Ask about the laboratory’s experience and accreditation.
- Consider the emotional and financial implications before proceeding.
For more information about PGT in Thailand, visit our PGT in Thailand page. You can also explore our guides and FAQ sections for additional insights.
Frequently asked questions
Can PGT-A and PGT-M be done at the same time?
Yes, PGT-A and PGT-M can be performed on the same embryo biopsy. This is often done when a couple has a known genetic mutation and also wants to screen for chromosomal abnormalities. However, not all clinics offer combined testing, so it's important to ask your provider.
Is PGT-A necessary for everyone doing IVF?
No, PGT-A is not necessary for everyone. It is typically recommended for women of advanced maternal age, those with recurrent pregnancy loss, or repeated implantation failure. Younger women with no known risk factors may not benefit significantly. Discuss your individual situation with your doctor.
What is the difference between PGT-A and PGT-SR?
PGT-A screens for an abnormal number of chromosomes (aneuploidy), while PGT-SR is used when a parent has a structural rearrangement of chromosomes, such as a translocation. PGT-SR detects embryos with unbalanced chromosomal rearrangements that could lead to miscarriage or birth defects.
How accurate is PGT-M?
PGT-M is highly accurate for the specific mutation it is designed to detect, with accuracy rates typically above 95%. However, there is a small risk of misdiagnosis due to technical limitations or genetic recombination. Confirmatory prenatal testing is often recommended.
Does PGT guarantee a healthy baby?
No, PGT does not guarantee a healthy baby. It can reduce the risk of transferring embryos with specific genetic issues, but it cannot detect all potential problems. Many factors affect pregnancy outcome, and prenatal testing is still recommended.
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Medical information notice: This article is educational and does not replace individual assessment, diagnosis, genetic counselling or treatment advice from a licensed clinician. Provider services, availability, fees and policies should be verified directly before booking.
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